Well with testing I can honestly say that on my campaign I forced it early with Kyoto being the final province required to make the push and it seemed a good way to take the initial brunt of RD and having a fully working citadel with all of its troop recruitment slots was VERY helpful in pushing my fight to near total victory.

My biggest headaches were naval power and I really regret not landing a strike force on the Chosokabe's main island to "liberate" them to help me out, strategically I had no interest in their island when my biggest battles were happening on the mainland and I am sure their navy would have been useful.

Still my biggest surprise was that Takeda strike force landing in the home provinces that really caught me off guards and was very well played by the AI.